Method of making an electrical contact for a color pickup tube

ABSTRACT

An electrical contact is made to one or more electrode layers on the inside surface of the faceplate assembly of a television camera by coating a conductive rivet with indium, inserting the rivet through a bore in faceplate assembly of the camera tube from the outside and flattening the end of the rivet coating which projects inside the tube to make contact with the electrode layer. The riveting takes place with a force sufficient to effect a hermetic seal between the rivet and the faceplate assembly of the camera tube.

United States Patent 1191 Tagawa Dec. 10, 1974 [54] METHOD OF MAKING AN ELECTRICAL 3,582,978 6/1971 Petersen 313/64 CONTACT FOR A COLOR PICKUP TUBE 3,665,239 5/1972 Morinaud et a1. 313/318 3,675,062 7/1972 Flasche 313/64 X [75] Inventor: Susumu Tagawa, Ka aga a, pan 3,714,488 1/1973 Kato 313/64 x Assigneez y Corporation, y Japan 3,721,752 3/1973 Kakizakl et a1 178/5.4 F

[ 1 Filedl 1972 Primary Examiner-James W. Lawrence 21 APPL No: 308 5 Assistant Examiner-Saxfield Chatmon, Jr.

Attorney, Agent, or Firm-Alvin Sinderb'rand; Lewis H. Eslinger [30] Foreign Application Priority Data Nov. 27, 1971 Japan 46-95639 57 ABSTRACT [52] us CL 313/318, 313/65 R 313/69 C An electrical contact is made to one or more elec- 313/92 BI 313/283 3135311 29/251 trode layers on the inside surface of the faceplate as- 59/2514 sembly of a television camera by coating a conductive 51 1111. c1 HOlj 5/48, H01 j 5/50 five with indium inserting the rivet hmugh a We in [58] Field of Search 313/318, 64 R 73 65 R faceplate assembly the camera tube from the 313/65 T 69 C 92 5 side and flattening the end of the rivet coating which 29/251, 5 4 projects inside the tube to make contact with the electrode layer. The riveting takes place with a force suffi- 1 References Cited cient to effect a hermetic seal between the rivet and the faceplate assembly of the camera tube. UNITED STATES PATENTS 2,928,968 3/1960 Hoagland 313/64 7 Claims, 10 Drawing Figures 3,040,124 6/1962 Camras 313/73 X 3,379,822 4/1968 Haans et a1. 313/64 X PATENTEL 3.854.069

- sum ear 3 METHOD OF MAKING AN ELECTRICAL CONTACT FOR A COLOR PICKUP TUBE BACKGROUND OF THE INVENTION The present invention relates to an electrical contact for use in a color television camera and a method for making such a contact and more particularly to a hermetically sealed conductive post which passes through the face of a television camera tube to contact a transparent electrode disposed on the interior face of the front plate of the television camera tube.

In some types of television cameras, for example the color television camera described in U.S. Pat. No. 3,688,021, issued Aug. 29, 1972, and in co-pending U.S. application Ser. No. 176,553, filed Aug. 31, 1971, both of which are assigned to the same assignee of this application, a transparent electrode is disposed on an interior glass face of a color television camera and an electrical contact is passed through the glass face to provide a current connection to the transparent electrode. Various methods exist in the prior art for establishing this current connection through the glass face of the camera to the interior transparent electrode. In one prior art method a glazed contact wire is inserted through a bore in an unpolished glass faceplate and is then fused to the faceplate. Thereafter the plate is polish-ground, including the projecting portions of the wire, and contacts are thereafter made to the fused wire. Various problems exist with this prior method particularly when a Nesa layer constitutes the interior transparent electrode. The deposition process for such a Nesa layer is strongly corrosive and the fused contact wire is thereby corroded. Furthermore the corrosive Nesa layer can creep into the inner space between the glass and the fused wire to oxidize the surface of the wire. Such fused wire connections are expensive and are often not vacuum tight.

In another prior method, such as described in US. Pat. No. 3,675,062, for example, a connection is made to the conductive Nesa layer by drilling a hole through the glass face and depositing the Nesa layer on the interior surface of the glass plate, including at least a portion of the hole through the glass. Thereafter an indium plug is inserted from the front side of the glass plate through the hole to contact the Nesa layer. In order to prevent subsequent corrosion of the indium plug from the outside it is necessary to first cover the exterior end of the indium plug with a neutral material such as a synthetic resin and then to penetrate the resin with a tack shaped steel plate to provide a current connection to the indium plug.

This method is relatively complicated, however, since each step must be done in sequence and the steps do not lend themselves to automatic, machine operated procedures. This results in poor quality control. Also it is typically necessary to counter-sink the bore in the glass plate in order to provide anchorage for the indium plug. However, the counter-sink may induce cracks in the front of the glass plate.

In still another prior method, as described in U.S. ap-

' plication Ser. No. 176,553 cited above, an indium bushing is fitted into the faceplate assembly hole and is deformed at its inner end to make contact with the electrode. A metal post is then fitted in the bushing. One problem with such a procedure is that difficulty is experienced in achieving a reliable hermetic sealing of the metal posts in the faceplate assembly. In order to overcome this difficulty the above-mentioned application discloses a relatively more complicated structure utilizing light sources and photoelectric transducers in place of the electrodes.

SUMMARY OF THE INVENTION The above and other disadvantages are overcome by the present invention of an improved electrical contact for use with an image signal pickup tube of the type having a transparent faceplate assembly which has an inner and outer surface and at least one hole passing through the assembly between them and an electrode disposed on its inner surface, the improved electrical contact of the invention including a metal post having a main portion whose diameter is less than the diameter of the faceplate hole and an enlarged head portion whose diameter is greater than the diameter of the faceplate hole, the main portion of the post being coated with a deformable metal. The coated main portion of the metal post is disposed in the faceplate hole and extends therethrough. A portion of the coating on the end of the metal post adjacent to the interior surface of the faceplate assembly is deformed to contact the electrode and to provide a hermetic seal against the electrode and the faceplate assembly interior surface. In one preferred embodiment the deformable metal coating is indium. The enlarged head portion of the metal post is disposed adjacent the exterior surface of the faceplate assembly. In some embodiments the end of the metal post which is adjacent the interior surfaces of the faceplate assembly is covered with a photoconductive layer.

The metal post is coated with the deformable metal, such as indium, by dipping the metal post, made of a material such as copper, into a heated bath comprised of a lower layer of liquid indium covered by an upper layer of non-volatilized glycerine or other type of alcohol compound having a high surface tension and then quickly withdrawing the indium coated post. Prior to the coating the metal post is prepared by stripping away,

its oxide layer with an acid, such as hydrochloric acid. When the metal post is lifted from the bath the indium adheres to the post but due to the surface tension of the glycerine the indium coating on the post is tapered at its lower end. The orientation of the post is such that the lower end corresponds to the main portion of the post whose diameter is less than the diameter of the faceplate hole.

It is therefore an object of the invention to provide an electrical contact for use with an image signal pickup tube which contact provides a hermetic seal with the faceplate of the image pickup tube.

It is another object of the invention to provide an electrical contact for use with the faceplate of an image signal pickup tube wherein the contact is constructed to be free from defects due to corrosion.

It is still another object of the invention to provide an electrical contact for use with the faceplate of an image pickup tube which may be assembled with the faceplate in a minimum number of steps. The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A, 1B, 1C and 1D show in sequence the method of making one embodiment of an electrical contact according to the invention;

FIG. 2 is a plan view showing the arrangement of the indexing electrodes on the faceplate assembly of an image pickup tube prior to the installation of an electrical contact according to the invention;

FIG. 3 is a sectional view taken generally along the line 33 of FIG. 2;

FIGS. 4A, 4B, 4C and 4D are sectional views illustrating the installation of an electrical contact in the faceplate assembly depicted in FIG. 2 by a method according to the invention.

DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS Referring now more particularly to FIGS. lA-ID, the successive steps manufacturing an electrical contact according to the invention are illustrated. The electrical contact comprises a metal post made of a conductive material such as copper. The post has a main portion 12 and an enlarged head portion 14. The oxide layer on the post 10 is first removed by an acid bath, such as a bath of hydrochloric acid.

Thereafter the post 10 is immersed in a heated bath contained in a beaker 22 having a lower layer of dissolved indium 16 covered by a layer of dissolved glycerine 18. The two layer bath is maintained at a temperature of less than 200 C. so that the glycerine is not allowed to volatilize. Preferably the bath is maintained at a temperature of approximately 180C. The purpose of using the layer of dissolved glycerine is to prevent the indium from being reacted with the atmosphere and also because the glycerine has a strong surface tension. In other embodiments of the method according to the invention glycol is substituted for glycerine. The bath is maintained at this temperature by a heater 20.

Referring now more particularlyto FIG. 1B the head portion. 14 of the metal post is temporarily affixed to the end of a rod 11 and is immersed in the bath until it reaches the indium layer. Thereafter the metal post is quickly lifted upwardly from the bath as illustrated in FIG. 1C. The surface of the main portion 12 of the post 10 is coated with a layer 24 of indium. Since the orientation of the post 10 when it is immersed and withdrawn from the bath is such that the enlarged head portion 14 is directed upwardly, the surface tension of the glycerine tapers the coating at the lower end. When the coated post reaches the atmosphere the indium coating is hardened. The coating is hermetically sealed to the post 10 as is illustrated in FIG. 10. The coated metal post is thus ready to be used in the form of a rivet by a technician who assembles the faceplate assembly of the image pickup tube.

Referring now more particularly to FIG. 2 the interior surface of the television camera faceplate assembly 25 is illustrated. The assembly initially has a transparent conductive layer, for example, of tin oxide, deposited over the entire area of the interior surface of a thin glass plate 26. The interior surface of the plate 26 is then subjected to photoetching to remove selected portions of the conductive layer so that the remaining portions form two interleaved, comb-shaped indexing electrodes A and B and a surrounding electrode C.

The surface of the glass plate 26 facing away from the electrodes A, B and C is bonded, as by adhesive, to a glass plate 28 which may have a striped color filter F formed thereon, for example (FIG. 3). Holes 30 are bored, by the use of ultrasonic waves for example, through the plates 26 and 28 at locations within the spines or bus-bar portions of the electrodes A and B and each receives a conductive post 10 of the type described with reference to FIGS. lA-lD in a manner to be described below.

Referring now more particularly to FIGS. 4A-4D there is shown in sectional view a portion of the faceplate assembly 25 of an image pickup tube in which the electrical contact of the invention is inserted. The metal post 10 coated with indium 24 has its main portion 12 inserted within the hole 30 in the faceplate assembly 25. The diameter of the main portion 12 of the electrical post 10 is smaller than the internal diameter of the hole 30. The diameter of the enlarged head portion 14 of the metal post is larger than the diameter of the faceplate hole 30 so that the head portion 14 of the metal post remains adjacent to the exterior surface of the glass plate 28. The indium coating is essentially a deformable metal and when the metal post 10 is inserted into the hole 30 with the desired force, for example from 2 to 3 Kg/cm the portion of the coating 24 around the enlarged head 14 hermetically seals the bore 30 at the juncture of the exterior surface of the glass plate 28 and the metal post 10.

The length of the metal post l0 is sufficient to project slightly beyond the interior surface of the faceplate assembly and the electrode A or B through the hole 30. This projecting end of the main portion 12 of the post 10 is next covered with a layer of polytetrafluroethylene (available commercially under the tradename Teflon) 32. Thereafter the Teflon sheet and the metal post 10 are subjected to a pressure of from 2 to 3 Kg/cm to spread the indium coating 24 over the Nesa layer A or B and to make an electrical contact be tween the coating 24 and the electrode layer A or B. This also hermetically seals the bore 30 between the metal post 10 and the electrodes A or B. The Teflon sheet 32 is thereafter removed and a photoconductive layer 34 (FIG. 4C) is vapor deposited over the electrodes A and B and the flattened indium coating 24.

The faceplate assembly is then attached and hermetically sealed to the main body 36 of the image pickup tube by a ring shaped indium layer 38 around the peripheral edges of the faceplate assembly 25. The indium layer 38 is covered with a ring electrode 40. In one preferred embodiment the ring electrode 40 and indium layer 38 are manufactured by stripping a stainless steel ring of its oxide coating and then dipping it in an indium-glycerine bath as described above with reference to FIGS. lA-lC to indium coat its inner surface. The indium coated ring electrode is thereafter attached to the outer, end edge of the main body 36 and the outer peripheral surface of the faceplate assembly by force fitting to effect the hermetic seal with the faceplate assembly 25.

The terms and expressions which have been employed here are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions, of excluding equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. An improved electrical contact for use with an image signal pickup tube of the type havng a transparent faceplate assembly, the faceplate assembly being provided with at least one hole passing from its exterior surface to its interior surface and having an electrode disposed on its interior surface, wherein the improvement comprises a metal post having a main portion whose diameter is less than the diameter of the faceplate assembly hole and an enlarged head portion whose diameter is greater than the diameter of the faceplate assembly hole; and a coating of electrically conductive, deformable material hermetically sealed to the main portion of the metal post and extending adjacent the enlarged head portion, the coated main portion of the metal post being disposed in the faceplate assembly hole and extending therethrough, a portion of the coating on the end of the metal post, nearest to the exterior surface of the faceplate assembly forming an hermetic seal at the juncture of said exterior surface and said metal post and a portion of the coating on the end of the metal post nearest to the interior surface of the faceplate assembly being deformed to extend outward over a portion of said interior surface so as to contact a surface of the electrode remote from said interior surface and to provide a hermetic seal.

2. An electrical contact as recited in claim 1 wherein the coating comprises indium.

3. An electrical contact as recited in claim 1 wherein the enlarged head portion of metal post is disposed adjacent to the faceplate assembly exterior surface.

4. An electrical contact as recited in claim 1 wherein a photoconductive layer covers the deformed portion of the coating which contacts the electrode.

5. A method of making an electrical contact with a conductive layer formed on a portion of a nonconductive substrate in an image signal pickup device comprising the steps of coating at least a portion of the external surface of a metal post with an electrically conductive, deformable material, boring a hole through the substrate, inserting the coated metal post into the substrate hole from the outside surface of the substrate and pressing the metal coated post at both ends with a predetermined force to hermetically seal the post coating with the interior surface of the hole, deforming a portion of the coating to contact conductive layer on the interior surface of the substrate and to form a hermetic seal therewith.

6. A method of making an electrical contact as recited in claim 5 wherein the step of coating the portion of the external surface of the metal post comprises the steps of immersing at least a main portion of the metal post in a heated bath containing a lower layer of dissolved indium and an upper layer of dissolved glycerine and forming a taper toward the lower end of the main portion of the metal post in the coating by withdrawing the indium coated metal post rapidly from the bath.

7. A method of making an electrical contact as recited in claim 6 wherein the step of coating the external surface of the metal post comprises the step of immersing at least a main portion of the metal post in a heated bath containing a layer of dissolved indium and an upper layer of dissolved glycol. 

1. An improved electrical contact for use with an image signal pickup tube of the type havng a transparent faceplate assembly, the faceplate assembly being provided with at least one hole passing from its exterior surface to its interior surface and having an electrode disposed on its interior surface, wherein the improvement comprises a metal post having a main portion whose diameter is less than the diameter of the faceplate assembly hole and an enlarged head portion whose diameter is greater than the diameter of the faceplate assembly hole; and a coating of electrically conductive, deformable material hermetically sealed to the main portion of the metal post and extending adjacent the enlarged head portion, the coated main portion of the metal post being disposed in the faceplate assembly hole and extending therethrough, a portion of the coating on the end of the metal post, nearest to the exterior surface of the faceplate aSsembly forming an hermetic seal at the juncture of said exterior surface and said metal post and a portion of the coating on the end of the metal post nearest to the interior surface of the faceplate assembly being deformed to extend outward over a portion of said interior surface so as to contact a surface of the electrode remote from said interior surface and to provide a hermetic seal.
 2. An electrical contact as recited in claim 1 wherein the coating comprises indium.
 3. An electrical contact as recited in claim 1 wherein the enlarged head portion of metal post is disposed adjacent to the faceplate assembly exterior surface.
 4. An electrical contact as recited in claim 1 wherein a photoconductive layer covers the deformed portion of the coating which contacts the electrode.
 5. A method of making an electrical contact with a conductive layer formed on a portion of a non-conductive substrate in an image signal pickup device comprising the steps of coating at least a portion of the external surface of a metal post with an electrically conductive, deformable material, boring a hole through the substrate, inserting the coated metal post into the substrate hole from the outside surface of the substrate and pressing the metal coated post at both ends with a predetermined force to hermetically seal the post coating with the interior surface of the hole, deforming a portion of the coating to contact conductive layer on the interior surface of the substrate and to form a hermetic seal therewith.
 6. A method of making an electrical contact as recited in claim 5 wherein the step of coating the portion of the external surface of the metal post comprises the steps of immersing at least a main portion of the metal post in a heated bath containing a lower layer of dissolved indium and an upper layer of dissolved glycerine and forming a taper toward the lower end of the main portion of the metal post in the coating by withdrawing the indium coated metal post rapidly from the bath.
 7. A method of making an electrical contact as recited in claim 6 wherein the step of coating the external surface of the metal post comprises the step of immersing at least a main portion of the metal post in a heated bath containing a layer of dissolved indium and an upper layer of dissolved glycol. 